Interchangeable lens, interchangeable lens system and camera system

ABSTRACT

An interchangeable lens is disclosed which prevents the camera body and interchangeable lens from being damaged even if an attempt is made to erroneously mount therebetween. The interchangeable lens is a second interchangeable lens whose flange back is the same as that of a first interchangeable lens and includes a protruding portion protruding from a mount reference surface. The protruding amount of the protruding portion is set when the second interchangeable lens has a specific phase relationship with a first camera, so that the protruding portion contacts a first wall portion of the first camera, and is set when the second interchangeable lens has a phase relationship with the first camera other than the specific phase relationship and a bayonet lug of the second interchangeable lens contacts a bayonet lug of the first camera, so that the protruding portion is away from the first wall portion.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to interchangeable lenses with differentamounts of protrusion from a mount reference surface toward an imageplane used for a camera system including a plurality of cameras havingthe same mount structure, and the camera system.

2. Description of the Related Art

With the advance of digitization of cameras in recent years, there is aproposal on a single-lens reflex camera system whose lenses areinterchangeable made up of single-lens reflex digital cameras whichinherit the sameness in a mount shape to allow conventionalinterchangeable lenses to be used on one hand, and which replace a 35 mmsilver-haloid film by an electronic image-pickup element such as a CCDsensor and CMOS sensor. However, an electronic image-pickup element suchas CCD sensor or CMOS sensor having the same size as the 35 mmsilver-haloid film is very expensive, and therefore the use of animage-pickup element (e.g., APS-C size image-pickup element) is becomingthe mainstream instead of the 35 mm film.

Since such a single-reflex digital camera using an image-pickup elementsmaller than a conventional 35 mm film has a smaller image circle thanthe 35 mm film, it is possible to reduce the size of a quick returnmirror in the camera body and consequently reduce the size of a camerabody itself. Furthermore, when the quick return mirror becomes smallerthan the conventional one, it is also possible to shorten the back focusof its interchangeable lens than the conventional interchangeable lensand its image circle is also small, which produces the merit ofdownsizing the interchangeable lens.

However, once the aforementioned short back-focus interchangeable lensis mounted on a 35 mm film camera body or a digital camera supporting animage circle larger than the interchangeable lens, the back end of theinterchangeable lens may interfere with the quick return mirror.Furthermore, allowing an interchangeable lens dedicated to a digitalcamera having a short back focus (with a small image circle) to bemounted on the camera body of a conventional system causes problems suchas a luminous flux failing to reach the periphery of the image-pickupsurface.

Therefore, there is a necessity for means for preventing the camera bodyand interchangeable lens from being mounted on such a combination.

Japanese Patent Publication No. 3217273 discloses a camera system,camera body and interchangeable lens which have a common mount butimposes restrictions on the mounting of interchangeable lenses having aback focus of a certain size or smaller. This camera system, etc.,provides a flange portion inside the mount of the conventional camerabody and restricts the mounting of the interchangeable lens by causing afixed protrusion provided on the interchangeable lens with a short backfocus to contact this flange portion.

However, in the camera system disclosed in Japanese Patent PublicationNo. 3217273, while the fixed protrusion on the lens side is in contactwith the flange portion on the camera side, if the user, being unawareof this fact, continues an operation of turning the interchangeable lenswith respect to the camera or pushing it against the camera, apossibility that the flange portion on the camera side or fixedprotrusion on the lens side may be damaged is undeniable.

SUMMARY OF THE INVENTION

It is one of objects of the present invention to provide aninterchangeable lens, interchangeable lens system and camera systemcapable of preventing, even when an attempt is made to mistakenly mountthe interchangeable lens in a camera in which the interchangeable lensis not mountable, the camera body and the interchangeable lens frombeing damaged and informing a user of the wrong mounting.

The interchangeable lens of the present invention as one aspect is asecond interchangeable lens used in a camera system including a firstinterchangeable lens, the second interchangeable lens, a first cameraand a second camera.

The second interchangeable lens includes a protruding portion whichprotrudes from a mount reference surface toward the image plane, theprotruding amount of which is larger than that of the firstinterchangeable lens and the second interchangeable lens has the sameflange back as that of the first interchangeable lens.

The first camera has a first wall portion inside its mount, the firstinterchangeable lens is mounted on the first camera through bayonetcoupling and the protruding portion of the second interchangeable lenscontacts the first wall portion, which prevents mounting of the secondinterchangeable lens portion.

The second camera includes a second wall portion provided at a positionretreated from the protruding portion of the second interchangeable lensinside its mount, the shape and dimensions of a bayonet lug are the sameas a bayonet lug of the first camera and the first and secondinterchangeable lens are mounted on the second camera through bayonetcoupling.

When a protruding amount of the protruding portion of the secondinterchangeable lens is set, in a case where the second interchangeablelens has a specific phase relationship with the first camera, so thatthe protruding portion of the second interchangeable lens contacts thefirst wall portion, and the protruding amount of the protruding portionof the second interchangeable lens is set, in a case where the secondinterchangeable lens has a phase relationship other than the specificrelationship with the first camera and an image plane side surface of abayonet lug of the second interchangeable lens is in contact with thebayonet lug of the first camera, so that the protruding portion of thesecond interchangeable lens is away from the first wall portion.

Furthermore, the interchangeable lens of the present invention asanother aspect is a second interchangeable lens whose flange back is thesame as that of the first interchangeable lens. The interchangeable lensincludes a protruding portion which protrudes from a mount referencesurface toward the image plane. The protruding amount of the protrudingportion is larger than that of the first interchangeable lens.

Furthermore, mounting of the second interchangeable lens in the firstcamera having a first wall portion inside its mount is prevented by theprotruding portion contacting the first wall portion. The first camerais a camera on which the first interchangeable lens is mounted throughbayonet coupling.

Furthermore, the second interchangeable lens is mounted on the secondcamera through bayonet coupling. The second camera is a camera whosebayonet lug has the same shape and dimensions as a bayonet lug of thefirst camera, the first interchangeable lens is mounted on the secondcamera through bayonet coupling and the second camera includes a secondwall portion provided at a position retreated from the protrudingportion of the second interchangeable lens inside its mount.

The protruding amount of the protruding portion of the secondinterchangeable lens is set, in a case where the second interchangeablelens has a specific phase relationship with the first camera, so thatthe protruding portion of the second interchangeable lens contacts thefirst wall portion, and set, in a case where the second interchangeablelens has a phase relationship other than the specific phase relationshipwith the first camera and an image plane side surface of a bayonet lugof the second interchangeable lens is in contact with the bayonet lug ofthe first camera, so that the protruding portion is away from the firstwall portion.

The interchangeable lens of the present invention as a further aspect isa second interchangeable lens used in a camera system including a firstinterchangeable lens, the second interchangeable lens, a first cameraand a second camera.

The second interchangeable lens comprises a protruding portionprotruding from a mount reference surface toward an image plane, theprotruding amount of the protruding portion is larger than that of thefirst interchangeable lens and the flange back of the secondinterchangeable lens is the same as that of the first interchangeablelens.

The first camera comprises a first wall portion inside its mount, thefirst interchangeable lens is mounted on the first camera throughbayonet coupling, and the protruding portion of the secondinterchangeable lens contacts the first wall portion, which preventsmounting of the second interchangeable lens. The first camera includes acamera-side index which serves as a mark for determining a phaserelationship with the first interchangeable lens when the firstinterchangeable lens is mounted thereon.

The second camera comprises a second wall portion provided at a positionretreated from the protruding portion of the second interchangeable lensinside its mount, is a camera whose bayonet lug has the same shape anddimensions as a bayonet lug of the first camera, and the first andsecond interchangeable lenses are mounted on the second camera throughbayonet coupling.

The second interchangeable lens comprises a lens-side index which servesas a mark for determining a phase relationship with the second camerawhen the second interchangeable lens is mounted on the second camera. Ina case where the second interchangeable lens has such a phaserelationship with the first camera that the lens-side index matches thecamera-side index, an image plane side surface of a bayonet lug of thesecond interchangeable lens contacts the bayonet lug of the firstcamera, preventing mounting of the second interchangeable lens on thefirst camera.

Furthermore, the interchangeable lens of the present invention as astill further aspect is a second interchangeable lens which has the sameflange back as that of the first interchangeable lens and which includesa protruding portion protruding from a mount reference surface toward animage plane.

Here, the protruding amount of the protruding portion is larger thanthat of the first interchangeable lens.

Furthermore, mounting of the second interchangeable lens on the firstcamera including a first wall portion inside its mount is prevented bythe protruding portion contacting the first wall portion. The firstcamera is a camera on which the first interchangeable lens is mountedthrough bayonet coupling and includes a camera-side index which servesas a mark for determining a phase relationship with the firstinterchangeable lens when the first interchangeable lens is mountedthereon.

Furthermore, the second interchangeable lens is mounted on the secondcamera through bayonet coupling. The second camera is a camera whosebayonet lug has the same shape and dimensions as a bayonet lug of thefirst camera, the first interchangeable lens is mounted on the firstcamera through bayonet coupling. The second camera includes a secondwall portion provided at a position retreated from the protrudingportion of the second interchangeable lens inside its mount.

Furthermore, the second interchangeable lens includes a lens-side indexwhich serves as a mark for determining a phase relationship with thesecond camera when the second interchangeable lens is mounted on thesecond camera.

When the second interchangeable lens includes such a phase relationshipwith the first camera that the lens-side index matches the camera-sideindex, an image plane side surface of a bayonet lug of the secondinterchangeable lens contacts the bayonet lug of the first camera, whichprevents the second interchangeable lens from being mounted on the firstcamera.

In addition, an interchangeable lens system can be made up by theabovedescribed interchangeable lens (second interchangeable lens) andthe above described first interchangeable lens for a camera groupincluding the abovedescribed first and second cameras.

Furthermore, the camera system of the present invention as a stillfurther aspect comprises a first interchangeable lens and a secondinterchangeable lens. The second interchangeable lens includes aprotruding portion protruding from a mount reference surface toward animage plane, the protruding amount of the protruding portion is largerthan that of the first interchangeable lens, and the flange back thereofis the same as that of the first interchangeable lens.

The camera system further comprises a first camera and a second camera.The first camera includes a first wall portion inside its mount. Thefirst interchangeable lens is mounted on the first camera throughbayonet coupling and the protruding portion of the secondinterchangeable lens contacting the first wall portion to therebyprevent mounting of the second interchangeable lens on the first camera.

The second camera includes a second wall portion provided at a positionretreated from the protruding portion of the second interchangeable lensinside its mount. The second camera is a camera whose bayonet lug hasthe same shape and dimensions as a bayonet lug of the first camera. Thefirst and second interchangeable lenses are mounted on the second camerathrough bayonet coupling.

The protruding amount of the protruding portion of the secondinterchangeable lens is set, in a case where the second interchangeablelens has a specific phase relationship with the first camera, so thatthe protruding portion of the second interchangeable lens contacts thefirst wall portion, and the protruding amount of the protruding portionof the second interchangeable lens is set, in a case where the secondinterchangeable lens has a phase relationship with the first cameraother than the specific phase relationship and an image plane sidesurface of a bayonet lug of the second interchangeable lens is incontact with the bayonet lug of the first camera, so that the protrudingportion of the second interchangeable lens is away from the first wallportion.

Furthermore, the camera system of the present invention as a stillfurther aspect comprises a first interchangeable lens and a secondinterchangeable lens. The second interchangeable lens has a largeramount of protruding portion protruding from a mount reference surfacetoward an image plane than that of the first interchangeable lens andhas the same flange back as that of the first interchangeable lens.

The camera system further comprises a first camera and a second camera.The first camera includes a first wall portion inside its mount, thefirst interchangeable lens is mounted on the first camera throughbayonet coupling. The protruding portion of the second interchangeablelens contacts the first wall portion to thereby prevent mounting of thesecond interchangeable lens on the first camera. The first camera has acamera-side index which serves as a mark for determining a phaserelationship with the first interchangeable lens when the firstinterchangeable lens is mounted thereon.

The second camera includes a second wall portion provided at a positionretreated from the protruding portion of the second interchangeable lensinside its mount, the second camera is a camera whose bayonet lug hasthe same shape and dimensions as a bayonet lug of the first camera. Thefirst and second interchangeable lenses are mounted on the second camerathrough bayonet coupling.

The second interchangeable lens includes a lens-side index which servesas a mark for determining a phase relationship with the second camerawhen the second interchangeable lens is mounted on the second camera.

In a case where the second interchangeable lens has such a phaserelationship with the first camera that the lens-side index matches thecamera-side index, an image plane side surface of a bayonet lug of thesecond interchangeable lens is in contact with the bayonet lug of thefirst camera to thereby prevent mounting of the second interchangeablelens on the first camera.

Furthermore, the interchangeable lens of the present invention as astill further aspect is not mountable on a first camera having a firstwall portion inside its mount, and is mountable on a second camerahaving a second wall portion inside its mount and including a bayonetlug having the same shape and dimensions as a bayonet lug of the firstcamera. And the interchangeable lens comprises a lens side mountincluding a lens-side bayonet lug corresponding to the bayonet lugs ofthe mounts of the first and second cameras and a protruding portionprotruding from a reference surface of the lens side mount toward animage plane. Herein, the protruding amount of the protruding portion isset, in a case where the interchangeable lens has a specific phaserelationship with the first camera, so that the protruding portioncontacts the first wall portion, and in a case where the interchangeablelens has a phase relationship with the first camera other than thespecific phase relationship and an image plane side surface of thebayonet lug of the interchangeable lens is in contact with the bayonetlug of the first camera, so that the protruding portion is away from thefirst wall portion.

The features of the interchangeable lens, interchangeable lens systemand camera system will become more apparent from the following detaileddescription of preferred embodiments of the invention with reference tothe drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a first interchangeable lens barrelaccording to Embodiment 1 of the present invention;

FIG. 2 is a cross-sectional view of a second interchangeable lens barrelaccording to Embodiment 1 of the present invention;

FIG. 3 is a cross-sectional view when the first interchangeable lensbarrel according to Embodiment 1 of the present invention is mounted ona first camera body;

FIG. 4 is a cross-sectional view when the first interchangeable lensbarrel according to Embodiment 1 of the present invention is mounted ona second camera body;

FIG. 5 is a cross-sectional view when the second interchangeable lensbarrel according to Embodiment 1 of the present invention is mounted onthe second camera body;

FIG. 6 is a cross-sectional view when an attempt is made to mount thesecond interchangeable lens barrel according to Embodiment 1 of thepresent invention in the first camera body;

FIG. 7 is a front view when the first interchangeable lens barrelaccording to Embodiment 1 of the present invention is mounted on thefirst camera body;

FIG. 8 is a front view when the second interchangeable lens barrelaccording to Embodiment 1 of the present invention is mounted on thesecond camera body;

FIG. 9 is a side view when the first interchangeable lens barrelaccording to Embodiment 1 of the present invention is mounted on thefirst camera body;

FIG. 10 is a side view when the second interchangeable lens barrelaccording to Embodiment 1 of the present invention is mounted on thesecond camera body;

FIG. 11 is a cross-sectional view showing a state in which a firstinterchangeable lens according to Embodiment 2 of the present inventionis mounted on a first camera body;

FIG. 12 is a cross-sectional view showing a state in which the firstinterchangeable lens according to Embodiment 2 of the present inventioncannot be mounted on a second camera body;

FIG. 13 is a cross-sectional view showing a state in which the secondinterchangeable lens according to Embodiment 2 of the present inventionis mounted on the first camera body;

FIG. 14 is a cross-sectional view showing a state in which the secondinterchangeable lens according to Embodiment 2 of the present inventionis mounted on the second camera body;

FIG. 15 is a cross-sectional view and a front view of the firstinterchangeable lens according to Embodiment 2 of the present invention;

FIG. 16 is a cross-sectional view and a front view of the secondinterchangeable lens according to Embodiment 2 of the present invention;

FIG. 17 is a cross-sectional view and a front view of the first camerabody according to Embodiment 2 of the present invention;

FIG. 18 is a cross-sectional view and a front view of the second camerabody according to Embodiment 2 of the present invention;

FIG. 19 is a perspective view of a first camera according to Embodiment3 of the present invention;

FIG. 20 is a perspective view of a second camera according to Embodiment3 of the present invention;

FIG. 21 is a side view of a first interchangeable lens according toEmbodiment 3 of the present invention;

FIG. 22 is a side view of a second interchangeable lens according toEmbodiment 3 of the present invention;

FIG. 23 is a perspective view of the second interchangeable lensaccording to Embodiment 3 of the present invention;

FIG. 24 is a cross-sectional view of the first interchangeable lensaccording to Embodiment 3 of the present invention;

FIG. 25 is a cross-sectional view of the second interchangeable lensaccording to Embodiment 3 of the present invention;

FIG. 26 is a cross-sectional view showing a state in which the firstinterchangeable lens according to Embodiment 3 of the present inventionis mounted on the first camera;

FIG. 27 is a cross-sectional view showing a state in which the secondinterchangeable lens according to Embodiment 3 of the present inventionis mounted on the second camera;

FIG. 28 is a cross-sectional view showing a state in which the secondinterchangeable lens according to Embodiment 3 of the present inventioncannot be mounted on the first camera;

FIG. 29 is a cross-sectional view showing a state in which the secondinterchangeable lens according to Embodiment 3 of the present inventioncannot be mounted on the first camera;

FIG. 30 is a cross-sectional view showing a state in which the firstinterchangeable lens according to Embodiment 3 of the present inventionis mounted on the second camera;

FIG. 31 is a front view showing a phase relationship between the bayonetlugs of the second interchangeable lens and the second camera accordingto Embodiment 3 of the present invention;

FIG. 32 is a front view showing a phase relationship between the bayonetlugs of the second interchangeable lens and the first camera accordingto Embodiment 3 of the present invention;

FIG. 33 is a front view showing a phase relationship between the bayonetlugs of the second interchangeable lens and the first camera accordingto Embodiment 3 of the present invention;

FIG. 34 is a front view showing a phase relationship between the bayonetlugs of the second interchangeable lens and the first camera accordingto Embodiment 3 of the present invention;

FIG. 35 is a front view showing a phase relationship between the bayonetlugs of the second interchangeable lens and the first camera accordingto Embodiment 3 of the present invention;

FIG. 36 is a cross-sectional view showing a state in which the secondinterchangeable lens according to Embodiment 3 of the present inventioncannot be mounted on the first camera;

FIG. 37 is a cross-sectional view of a mount provided on the secondinterchangeable lens according to Embodiment 3 of the present invention;

FIG. 38 is a cross-sectional view showing a modification example of themount provided on the second interchangeable lens according toEmbodiment 3 of the present invention;

FIG. 39 is a perspective view showing a modification example of themount provided on the second interchangeable lens according toEmbodiment 3 of the present invention;

FIG. 40 is a perspective view showing a modification example of themount provided on the second interchangeable lens according toEmbodiment 3 of the present invention; and

FIG. 41 is a perspective view showing a modification example of themount provided on the second interchangeable lens according toEmbodiment 3 of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference now to the attached drawings, embodiments of the presentinvention will be explained below.

[Embodiment 1]

FIG. 1 to FIG. 6 show a camera system including an interchangeable lensand camera body which is Embodiment 1 of the present invention.

FIG. 1 is a cross-sectional view showing a first interchangeable lens 1for a 35 mm film camera, which holds a first optical lens 2 and a secondoptical lens 3 in a lens barrel. On the back end side, bayonet lugs 4for bayonet coupling with a camera body are provided and the bayonetlugs 4 are disposed closer to an image-pickup surface 100 than a mountreference surface 5 located at a distance of a flange back “A” from theimage-pickup surface 100. Here, the portion protruding from the mountreference surface 5 including the bayonet lug 4 toward the image-pickupsurface corresponds to the protruding portion of the firstinterchangeable lens 1.

Furthermore, the distance from the mount reference surface 5 to the endface of the bayonet lug 4 on the image-pickup surface 100 side isrepresented by “B′”. Furthermore, the distance from the image-pickupsurface 100 to the second optical lens 3 is represented by “C′”. Here,the camera system is constructed so as to secure A−B′<C′ to prevent thesecond optical lens 3 from being damaged when the first interchangeablelens 1 is singly placed on a desk, etc.

FIG. 2 is a cross-sectional view schematically showing a secondinterchangeable lens 11 for a camera provided with an APS-C sizeimage-pickup element (however, any image-pickup element of the sizewhich is different from the APS-C size is also acceptable if it issmaller than the 35 mm film size), which holds a first optical lens 12and a second optical lens 13 in a lens barrel. On the back end side ofthe second interchangeable lens 11, bayonet lugs 4 for bayonet couplingwith a camera body as in the case of the first interchangeable lens 1are provide and the bayonet lugs 4 are disposed closer to animage-pickup surface 100 than a mount reference surface 5 located at adistance of a flange back “A” from the image-pickup surface 100.

Furthermore, a protruding portion 14 is formed closer to theimage-pickup surface 100 than the bayonet lugs 4 and on the innerdiameter side of the bayonet lugs 4. The portion from the mountreference surface 5 to the end face of the protruding portion 14 on theimage-pickup surface 100 side corresponds to the protruding portionaccording to the present claims, but the portion protruding from thebayonet lug 4 will be referred to as a “protrusion” for convenience ofexplanation here. At the end (back end) of the protruding portion 14, arubber ring 15, which is an elastic member, is fitted in on the entirecircumference centered on the optical axis by means of its elasticity.Furthermore, the rubber ring 15 has a color tone and material differentfrom those of the protruding portion 14, which allows the user to easilyvisually recognize the rubber ring 15.

Here, suppose the distance from the mount reference surface 5 to the endface of the rubber ring 15 on the image-pickup surface 100 side is “B”.

The second optical lens 13 is disposed closer to the image-pickupsurface 100 compared to the first interchangeable lens 1 so as to takeadvantage of the protruding portion 14 and is constructed so as toshorten a back focus “C”. Furthermore, as in the case of the firstinterchangeable lens 1, the camera system is constructed so as to secureA−B<C to prevent the second optical lens 13 from being damaged when thesecond interchangeable lens 11 is singly placed on a desk, etc.

Furthermore, to prevent the camera system from tipping over even whenthe camera system is placed with the protruding portion 14 face down ona desk, etc., the ratio of the diameter of the protruding portion 14 tothe protruding amount of protruding portion 14 is set to 3:1 or more andthe rubber ring 15 also has the effect as a non-slip member.

When the first interchangeable lens 1 is compared with the secondinterchangeable lens 11, both lenses have the same distance “A” from theimage-pickup surface 100 to the mount reference surface 5 and have thebayonet lug 4 formed at the same position and in the same shape. Theprotruding amount from the reference surface 5 toward the image-pickupsurface 100 is designed to be “B′”<(B) and the back focuses from theimage-pickup surface 100 to the respective second optical lenses aredesigned to be “C′”>(C)

FIG. 3 is a schematic cross-sectional view showing a state in which thefirst interchangeable lens 1 is mounted on a first camera body 21 (e.g.,a camera body for a 35 mm film) which allows mounting of only the firstinterchangeable lens 1. The first camera body 21 is provided with amount reference surface 22 on the camera body side which contacts themount reference surface 5 of the first interchangeable lens 1 and abayonet structure 23 on the camera body side which engages with thebayonet lug 4.

Reference numeral 24 denotes a quick return mirror and the quick returnmirror 24 reflects part of a luminous flux which has passed through thefirst optical lens 2 and the second optical lens 3 to a finder system(not shown) and sends the rest of the luminous flux to a distancemeasuring system and photometric system (not shown) through asemitransparent portion. When the user performs a release operation, thequick return mirror 24 moves up in the direction indicated by an arrowin the figure.

FIG. 4 is a schematic cross-sectional view showing a state in which thefirst interchangeable lens 1 is mounted on a second camera body 31(e.g., a camera body provided with an APS-C size image-pickup element)which allows mounting of the first interchangeable lens 1 and secondinterchangeable lens 11.

As in the case of the first camera body 21, the second camera body 31 isprovided with a mount reference surface 22 on the camera body side whichcontacts the mount reference surface 5 of the first and secondinterchangeable lenses 1 and 11, and a bayonet structure 23 on thecamera body side which engages with the bayonet lug 4.

Reference numeral 32 denotes a quick return mirror and the quick returnmirror 32 reflects part of a luminous flux which has passed through thefirst optical lens 2 and the second optical lens 3 to a finder system(not shown) and sends the rest of the luminous flux to a distancemeasuring system and photometric system (not shown) through asemitransparent portion. When the user performs a release operation, thequick return mirror 32 moves up in the direction indicated by an arrowin the figure.

Here, the quick return mirror 32 is the same as the quick return mirror24 of the first camera body 21 in terms of functions and operations, butsince the image-pickup element is smaller than a 35 mm film, the quickreturn mirror 32 can be smaller than the quick return mirror 24 and evenwhen quick return mirror 32 moves up, the track thereof is small.

FIG. 5 is a schematic cross-sectional view when the secondinterchangeable lens 11 is mounted on the second camera body 31. Thesecond camera body 31 is provided with a recess portion 33 to avoid theprotruding portion 14 of the second interchangeable lens 11.Furthermore, since the quick return mirror is small as described above,even the second interchangeable lens 11 which is an interchangeable lenswith a short back focus does not interfere with the quick return mirror32 and the track thereof is designed to pass closer to the image-pickupsurface 100 than the back end face (second wall portion) of the recessportion 33 which is provided at apposition where the distance from themount reference surface 22 on the camera body side is “F”.

FIG. 6 is a schematic cross-sectional view when an attempt is made tomount the second interchangeable lens 11 on the first camera body 21. Inthis combination, since the second interchangeable lens 11 is for acamera provided with an APS-C size image-pickup element, a wall portion(first wall portion) 25 is provided at a position at a shorter distance“F′” from the mount reference surface 22 of the first camera body 21than the distance “B” from the mount reference surface 5 to the end faceof the rubber ring 15 (protrusion 14) on the image-pickup surface 100side so as to prevent the second interchangeable lens 11 from beingmounted on the first camera body 21 which is a 35 mm film camera. Atthis time, even when a user who is unaware of fact that mounting is notpossible attempts to forcibly mount the second interchangeable lens 11,the rubber ring 15 is designed to contact the wall portion 25 of thefirst camera body 21 to prevent both the first camera body 21 and thesecond interchangeable lens 11 from being damaged.

Furthermore, an embodiment for preventing such wrong mounting will beexplained using FIG. 7 to FIG. 10.

FIG. 7 is a front view of the first interchangeable lens 1 mounted onthe first camera body 21. The first camera body 21 is provided with amounting index 26 to match the phase of the bayonet lug 4 when the firstinterchangeable lens 1 is mounted and the first interchangeable lens 1is provided with a mounting index 6. When the first interchangeable lens1 is mounted, the mounting is completed by matching the phase of themounting index 6 with the phase of the mounting index 26, allowing therespective mount reference surfaces to contact each other and turningthe first interchangeable lens 1 by a predetermined angle “D”.

FIG. 8 is a front view showing the second interchangeable lens 11mounted on the second camera body 31 The second interchangeable lens 11is provided with a mounting index 16 for matching the phase of thebayonet lug 4 with respect to the second camera body 31 at an anglephase “E” which is different from the mounting index 6 of the firstinterchangeable lens 1. Furthermore, the second camera body 31 isprovided with a mounting index 35 at an angle phase corresponding to themounting index 16 of the second interchangeable lens 11. Furthermore,since the second camera body 31 can also mount the first interchangeablelens 1, the second camera body 31 is also provided with a mounting index34 corresponding to the mounting index 6 of the first interchangeablelens 1.

Furthermore, as shown in FIG. 8, making the shape of the mounting index34 corresponding to the first interchangeable lens 1 different from theshape of the mounting index 35 corresponding to the secondinterchangeable lens 11 visually alerts the user making it possible tofurther prevent wrong mounting and if a difference is provided in notonly the shape but also color tone, a larger effect can be expected.When the interchangeable lens is mounted, the mounting is completed bymatching the phases of the respective mounting indices and turning theinterchangeable lens by a predetermined angle “D”.

Furthermore, as shown in FIG. 9 and FIG. 10, further effects can beexpected if the shapes and color tones of the mounting index 6 of thefirst interchangeable lens 1 and the mounting index 16 of the secondinterchangeable lens 11 match with the mounted indexes 34 and 35 of thefirst camera body 21 and second camera body 31, respectively.Furthermore, adopting a shape protruding from the circumference of thesecond interchangeable lens 11 for the mounting index 16 can alert theuser with a tactile sense and further prevent wrong mounting.

[Embodiment 2]

Using FIG. 11 to FIG. 18, a camera system which is Embodiment 2 of thepresent invention will be explained. FIG. 11 to FIG. 14 arecross-sectional views showing main parts of the camera system. FIG. 15and FIG. 16 are cross-sectional views and front views showing first andsecond interchangeable lenses of this embodiment. FIG. 17 and FIG. 18are cross-sectional views and front views showing the first and secondcamera bodies of this embodiment.

Reference numerals 120 and 130 denote interchangeable lenses, 120denotes a second interchangeable lens having a small image size on thefilm surface (or photoreceiving surface of an image-pickup element) and130 denotes a first interchangeable lens having a large image size.Reference numerals 140 and 150 denote camera bodies, 140 denotes asecond camera body which allows mounting of the first and secondinterchangeable lenses 130, 120 and 150 denotes a first camera bodywhich does not allow mounting of the second interchangeable lens 120.FIG. 11 shows a state in which the second interchangeable lens 120 ismounted on the second camera body 140 and FIG. 12 shows a state in whichthe second interchangeable lens 120 cannot be mounted on the firstcamera body 150. FIG. 13 shows a state in which the firstinterchangeable lens 130 is mounted on the second camera body 140 andFIG. 14 shows a state in which the first interchangeable lens 130 ismounted on the first camera body 150.

FIG. 15 shows the second interchangeable lens 120, reference numeral 101denotes an interchangeable lens body and 102 denotes a lens-side bayonetmount. In the lens-side bayonet mount 102, reference numeral 102 adenotes a mount reference surface, 102 b denotes a lug (bayonet lug) forbayonet coupling with the camera-side mount, and a plurality of bayonetlugs are provided in the circumferential direction. Reference numeral103 denotes a back cover (protruding portion). The back end face of theback cover 103 on the camera side has a larger protruding amount fromthe mount reference surface 102 a (indicated by A in the figure) thanthat of the first interchangeable lens 130 which will be describedlater. Reference numeral 104 denotes damage prevention rubber, 105denotes a lens-side electric contact. Since the interchangeable lensbody 101 is not directly related to this proposal, only its outline isexpressed and detailed explanations thereof will be omitted.

FIG. 16 shows the first interchangeable lens 130, reference numeral 106denotes an interchangeable lens body and 107 denotes a back cover. Alens-side bayonet mount 102 and a lens-side electric contact 105 are thesame as those of the second interchangeable lens 120. In the lens-sidebayonet mount 102, reference numeral 102 a denotes a mount referencesurface, 102 b denotes a lug (bayonet lug) for bayonet coupling with thecamera-side mount and a plurality of bayonet lugs are provided in thecircumferential direction.

FIG. 17 shows a cross-sectional view and a front view of the secondcamera body 140. Reference numeral 108 denotes a camera main body, 109denotes a bayonet mount on the camera body side, 110 denotes a pluralityof electric contact pins on the camera side and 111 denotes a contactpin spring. The bayonet mount on the camera body side 109 is providedwith a mount reference surface 109 a which is a positioning surface withrespect to the interchangeable lens and bayonet lugs on the camera side109 b. The electric contact pins 110 are biased by the contact pinspring ill at positions corresponding to the electric contacts on theinterchangeable lens side 105 toward the interchangeable lens.

FIG. 18 shows a cross-sectional view and front view of the first cameramain body 150. Reference numeral 112 denotes a camera body. The bayonetmount on the camera body side 109, electric contact pins 110 and contactpin spring 111 are the same as those of the second camera body in FIG.17. In the inner diameter portion of the mount of the camera body 112 isa first wall portion 112 a. In FIG. 17, in the mount inner diameterportion of the camera main body 108 of the second camera body 140, anotch portion 108 a which can contain the back cover 103 of the secondinterchangeable lens 120 is formed at the position corresponding to thefirst wall portion 112 a of the first camera body 150.

In FIG. 15, suppose the distance in the direction of the optical axisfrom the mount reference surface 102 a of the second interchangeablelens 120 to the back end face of the second interchangeable lens 120 onthe camera side is “A”.

FIG. 16, suppose the distance in the direction of the optical axis fromthe mount reference surface 102 a of the first interchangeable lens 130to the back end face of the first interchangeable lens 130 on the cameraside is “B” (<A).

In FIG. 17, suppose the distance in the direction of the optical axisfrom the mount reference surface 109 a of the second camera body 140 tothe back end face of the notch portion 108 a is “C”.

In FIG. 18, suppose the distance in the direction of the optical axisfrom the mount reference surface 109 a of the first interchangeable lens150 to the first wall portion 112 a is “D”.

In FIG. 15 and FIG. 16, suppose the distance in the direction of theoptical axis from the mount reference surface 102 a of the second andfirst interchangeable lenses 120, 130 to the end face (right end face inthe figure) on the camera side of the bayonet lug 120 b of the lensmount is “E”.

In FIG. 17 and FIG. 18, suppose the distance in the direction of theoptical axis from the mount reference surface 109 a of the second andfirst camera bodies 140, 150 to the end face (left end face in thefigure) on the lens side of the bayonet lug 109 b of the mount on thecamera side is “F”.

In FIG. 15 and FIG. 16, suppose the distance in the direction of theoptical axis from the mount reference surface 102 a of the second andfirst interchangeable lenses 120, 130 to the contact surface 105 a ofthe electric contact 105 is “G”.

In FIG. 17 and FIG. 18, suppose the distance in the direction of theoptical axis from the mount reference surface 109 a of the second andfirst camera bodies 140, 150 to the end of the electric contact pins onthe camera side 110 when the interchangeable lens is not mounted yet is“H”.

In FIG. 11, “A” must be larger than “C” so that the secondinterchangeable lens 120 can be mounted on the second camera body 140.

In FIG. 12, “A” must be smaller than “D” so that the secondinterchangeable lens 120 is prevented from being mounted on the firstcamera body 150.

In FIG. 13 and FIG. 14, C and D must be larger than “B” so that thefirst interchangeable lens 130 can be mounted on the first and secondcamera bodies 150, 140.

When all that has been described above is expressed using symbols in thefigures, C>A>D>B must be satisfied so that mounting of theinterchangeable lens on the camera body is selectively enabled/disabled.

In FIG. 12, when the second interchangeable lens 120 cannot be mountedon the first camera body 150, preventing the second interchangeable lens120 from turning unnecessarily with respect to the first camera body 150requires that the bayonet lug 102 b of the mount of the secondinterchangeable lens 120 be located within the angle phase where thebayonet lug 109 b of the mount of the first camera body 150 does notexist and at the same time the bayonet lug of the second interchangeablelens 120 and the first camera 150 exist at the same position in thedirection of the optical axis. When this condition is expressed usingsymbols in the figures, E−F>A−D and D>E must be satisfied.

In other words, when the above described conditions are satisfied, in astate in which the bayonet lug 102 b of the mount of the secondinterchangeable lens 120 does not locate within a certain angle phasewhere the bayonet lug 109 b of the mount of the first camera body 150does not exist and the end face on the camera side of the bayonet lug102 b contacts the end face on the lens side of the bayonet lug 109 b,the back end face on the camera side of the back cover 103 of the secondinterchangeable lens 120 draws away from the first wall portion 112 a ofthe first camera body 150 by an amount substantially corresponding tothe thickness of the bayonet lug 102 b.

Furthermore, in FIG. 12, when the second interchangeable lens 120 cannotbe mounted on the first camera body 150, if an attempt is made to mountthe second interchangeable lens 120 on the camera body 150 although thesecond interchangeable lens 120 is actually unmountable, (A−D)>(G−H)>0must be satisfied when expressed using symbols in the figures as thecondition for protecting the electric contact pins 110 on the firstcamera body 150 side and the electric contact pins 105 on theinterchangeable lens 120 side from interference with the back end of theinterchangeable lens 120 or damage caused by interference, etc.

Therefore, by setting dimensions satisfying the above describedconditional expressions, in a camera system having the same flange backfrom a mount reference surface to a film surface (or photoreceivingsurface of an image-pickup element) and comprising first and secondcamera bodies whose mounts on the body side have the same shape and aplurality of interchangeable lenses having a common mount on the lensside which engages with the mount on the camera body side, it ispossible to select the mountable interchangeable lenses on the camerabody side, to prevent unnecessary damage to the camera body and theinterchangeable lens in combinations of unmountable interchangeablelenses and camera bodies, and to reliably protect electric contacts forcommunication of electric signals and power supply between the camerabody and the interchangeable lens.

[Embodiment 3]

With new reference numerals assigned to the structure of theinterchangeable lenses and cameras explained in Embodiment 1 andEmbodiment 2, Embodiment 3 will be explained using FIG. 19 to FIG. 41 indetail below. Here, a case where the first and second cameras aredigital cameras provided with an image-pickup element will be explained.In the following explanations, “front” means an object side and “back”will refer to an image plane or image-pickup element side.

FIG. 19, FIG. 26, FIG. 28 and FIG. 29 show a first camera (camera body)201. The first camera 201 is provided with a ring-shaped mount 202 formounting a first interchangeable lens, which will be described later, onthe front. The front end face of this mount 202 constitutes a referencesurface (mount reference surface) 202 a when a first interchangeablelens is mounted.

Inside the mount 202 (inner diameter side), bayonet lugs 203 for bayonetcoupling with the first interchangeable lens are formed at threelocations in the circumferential direction at a certain distance behindthe mount reference surface 202 a.

At a certain distance behind the positions at which these bayonet lugs203 are provided, a wall portion (first wall portion) 205 which crossesthe optical axis L (see FIGS. 26, 28 and 29) at right angles, that is,which is parallel to the mount reference surface 202 a, is formed aspart of a mirror box. Inside this wall portion 205, a square opening isformed, a quick return mirror 206 is disposed at a certain distancebehind the opening and an image-pickup element 210 made up of a CCD orCMOS sensor is fixed behind the quick return mirror 206 (see FIG. 26,FIG. 28 and FIG. 29). The quick return mirror 206 rotates behind thewall portion 205.

Furthermore, a plurality of electric contact pins 204 are provided inthe lower part of the wall portion 205. These electric contact pins 204are used for communication with the first interchangeable lens mountedand power supply to the first interchangeable lens.

As shown in FIG. 19, at the top of the front end face of the mount 202,a red, circular camera-side index (hereinafter referred to as “lensmounting index”) 208 is provided. The lens mounting index 208 serves asa mark to match the phase of bayonet lugs of the first interchangeablelens with the phase (between neighboring bayonet lugs 203 in thecircumferential direction) of the first camera 201 where the bayonetlugs 203 do not exist when the first interchangeable lens isbayonet-coupled.

FIG. 20, FIG. 27 and FIG. 30 show a second camera (camera body) 301. Onthe front of the second camera 301, a ring-shaped mount 302 to mount afirst and second interchangeable lenses which will be described later isprovided. The front end face of this mount 302 serves as a referencesurface (mount reference surface) 302 a when the first and secondinterchangeable lenses are mounted.

Inside the mount 302 (inner diameter side), bayonet lugs 303 for bayonetcoupling with the first and second interchangeable lenses are formed atthree locations in the circumferential direction at a certain distancebehind the mount reference surface 302 a.

At a certain distance behind the positions where these bayonet lugs 303are provided, a wall portion 305 which crosses the optical axis L (seeFIGS. 27 and 30) at a right angle, that is, which is parallel to themount reference surface 302 a, is formed as part of a mirror box. Here,the distance from the mount reference surface 302 a to the wall portion305 is the same as the distance from the mount reference surface 202 ato the wall portion 205 in the first camera 201 (indicated by F′ in FIG.28).

Inside this wall portion 305, a containing portion 307 capable ofcontaining a protruding portion provided on the back end side of thesecond interchangeable lens, which will be described later, is provided.This containing portion 307 is concave-shaped recessed backward from thewall portion 305, and a square opening is formed on the back end face(second wall portion) 307 a of the containing portion 307.

Then, a quick return mirror 306 is disposed at a certain distance behindthe square opening, and an image-pickup element 310 such as a CCD sensoror CMOS sensor is fixed behind the quick return mirror 306 (see FIG. 27and FIG. 30).

Here, for the second camera 301 of this embodiment, the image-pickupelement 310 which is smaller than the image-pickup element 210 of thefirst camera 201 is used to adapt to a smaller image circle than thefirst camera 201. For this reason, a mirror which is smaller than thequick return mirror 306 in the first camera 201 is used for the quickreturn mirror 306, too, and the quick return mirror 306 rotates behindthe back end face 307 a of the containing portion 307. Downsizing of thequick return mirror 306 and image-pickup element 310 allows downsizingof the entire second camera 301 compared to the first camera 201.

A plurality of electric contact pins 304 are provided in the lower partof the wall portion 305. These electric contact pins 304 are used forcommunication with the first and second interchangeable lenses mountedand for power supply to these interchangeable lenses.

Furthermore, as shown in FIG. 20, at the top of the front end face ofthe mount 302, a red, circular camera-side index (hereinafter referredto as “first lens mounting index”) 308 is provided. The first lensmounting index 308 serves as a mark to match the phase of the bayonetlugs of the first interchangeable lens with the phase (betweenneighboring bayonet lugs 303 in the circumferential direction) of thesecond camera 301 where the bayonet lugs 303 do not exist when the firstinterchangeable lens is bayonet-coupled.

Furthermore, outside the mount 302 on the front of the second camera301, a white, rectangular camera-side index (hereinafter referred to as“second lens mounting index”) 309 is provided. The second lens mountingindex 309 serves as a mark to match the phase of the bayonet lug of thesecond interchangeable lens with the phase (between neighboring bayonetlugs 303 in the circumferential direction) of the second camera 301where the bayonet lugs 303 do not exist when the second interchangeablelens is bayonet-coupled.

FIG. 21 and FIG. 24 show a first interchangeable lens 401. Inside thefirst interchangeable lens 401, a first optical lens 411 and a secondoptical lens 412 are arranged in order from the front side. Note thatthe figure shows only two optical lenses, but other optical lensesactually exist between these optical lenses.

A ring-shaped mount 402 is disposed on back side of the firstinterchangeable lens 401. The back end face of the outermost part of themount 402 serves as a reference surface (mount reference surface) 402 awhen mounted on the first and second cameras 201, 301.

Furthermore, the portion on the inner diameter side of the mountreference surface 402 a of the mount 402 has a backward protruding shapeand bayonet lugs 403 capable of engaging with the bayonet lugs 203, 303of the first and second cameras 201, 301 are formed at three locationson the circumference of the back end of this protruding portion. Theback end face of this bayonet lug 403 constitutes the back end face ofthe first interchangeable lens 401.

Furthermore, at the lower part of the back end face of the firstinterchangeable lens 401, a plurality of electric contacts 404 tocommunicate with the first and second cameras 201, 301 and to receive apower supply from these cameras are provided. These electric contacts404 are provided at positions slightly protruding backward from the backend face of the first interchangeable lens 401, but the protrudingamount of these electric contacts 404 will be ignored in the followingexplanations.

Furthermore, in the innermost diameter portion of the mount 402, asecond optical lens 412 is fixed via a lens holding member 413. However,the second optical lens 412 may be fixed as shown in the figure or mayalso be movable in the direction of the optical axis.

Furthermore, as shown in FIG. 21, at the back on the outer surface ofthe first interchangeable lens 401, a red, circular lens-side index(hereinafter referred to as “first lens-side index”) 408 is provided.The first lens-side index 408 serves as a mark to match the phase of thebayonet lugs 403 of the first interchangeable lens 401 with the phase ofthe first and second cameras 201, 301 where the bayonet lugs 203, 303 donot exist when the first interchangeable lens 401 is bayonet-coupledwith the first and second cameras 201, 301.

FIGS. 22, 23 and 25 show a second interchangeable lens 501. Inside thesecond interchangeable lens 501, a first optical lens 511 and a secondoptical lens 512 are arranged in order from the front side. Note thatthe figure shows only two optical lenses, but other optical lensesactually exist between these optical lenses.

A ring-shaped mount 502 which is also shown in FIG. 37 is disposed atthe back of the second interchangeable lens 501. The back end face onthe outermost part of the mount 502 serves as a reference surface (mountreference surface) 502 a when mounted on the second camera 301.

Furthermore, the portion on the inner diameter side of the mountreference surface 502 a of the mount 502 has a shape protruding by theprotruding amount larger than the amount of backward protrusion from themount reference surface 402 a in the first interchangeable lens 401.

At three locations on the circumference in an intermediate position inthe direction of the optical axis of this protruding portion, bayonetlugs 503 are formed, which can engage with the bayonet lugs 303 of thesecond camera 301. Here, the distance from the mount reference surface502 a to the back end face of the bayonet lugs 503 is the same as thedistance from the mount reference surface 402 a to the back end face ofthe bayonet lugs 403 of the first interchangeable lens 401.

Furthermore, the portion on the inner diameter side of the bayonet lugs503 of the mount 502 further protrudes backward. Note that the portionfrom the mount reference surface 502 a to the back end face of theportion protruding backward from the bayonet lugs 503 corresponds to theprotruding portion described in the present claims, but the portionprotruding backward from the bayonet lugs 503 is referred to as theprotruding portion 505 for convenience of explanation here. As shown inFIG. 25, the protruding amount B from the mount reference surface 502 aon the back end face of the protruding portion 505 is larger than theprotruding amount B′ backward from the mount reference surface 402 a inthe first interchangeable lens 401 shown in FIG. 24. Here, the settingof the protruding amount B of the protruding portion 505 will bedescribed later.

In the innermost diameter portion of this protruding portion 505, asecond optical lens 512 is fixed via a lens holding member 513. However,the second optical lens 512 may be fixed as shown in the figure or mayalso be movable in the direction of the optical axis within an areaincluding the inner space of the protruding portion 505.

Here, as shown in FIG. 24 and FIG. 25, the flange back “A” which is thedistance from the mount reference surface 402 a of the firstinterchangeable lens 401 to the image-pickup surface (photoreceivingsurface of the image-pickup elements 210, 310) 100 is equal to theflange back “A” which is the distance from the mount reference surface502 a of the second interchangeable lens 501 to the image-pickup surface(photoreceiving surface of the image-pickup element 310) 100.

Furthermore, the back focus “C” shown in FIG. 25 which is the distancefrom the second optical lens 512 in the second interchangeable lens 501to the image-pickup surface 100 is shorter than the back focus “C′”which is the distance from the second optical lens 412 in the firstinterchangeable lens 401 to the image-pickup surface 100. Such a shortback focus is advantageous in the optical design for widening the fieldangle of the second interchangeable lens 501. Moreover, since the imagecircle of the second camera 301 on which the second interchangeable lens501 is mounted is reduced as described above, the size of the quickreturn mirror 306 can be reduced.

However, to enable normal telephoto image taking, the firstinterchangeable lens 201 is also designed to be mountable on the secondcamera 301. Therefore, the first interchangeable lens 201 which can bemounted on the first camera 201 can be used effectively for the secondcamera 301, too.

Further, as shown in FIG. 22, 23, at the back on the outer surface ofthe second interchangeable lens 501, a white, rectangular lens-sideindex (hereinafter referred to as “second lens-side index”) 509 isprovided. The second lens-side index 509 serves as a mark to match thephase of the bayonet lugs 503 of the second interchangeable lens 501with the phase of the second camera 301 where the bayonet lugs 303 donot exist when the second interchangeable lens 501 is bayonet-coupledwith the second camera 301.

Here, the phase of the position at which the second lens-side index 509in the second interchangeable lens 501 is provided with respect to thebayonet lugs 503 differs from the phase at the position at which thefirst lens-side index 408 is provided in the first interchangeable lens401 with respect to the bayonet lugs 403 by approximately 20 degrees.

Furthermore, as shown in FIG. 37, too, a plurality of electric contacts504 are held in the mount 502, and these electric contacts 504 areexposed slightly backward from the bayonet lugs 503 (however, ahead ofthe back end face of the protruding portion 505).

Furthermore, the mount structures (shape and dimensions) of the firstcamera 201 and the second camera 301 explained in this embodiment aremutually identical including the shape and dimensions of the bayonetlugs 203 and 303. Furthermore, the mount structures (shape anddimensions) of the first interchangeable lens 401 and the secondinterchangeable lens 501 are mutually identical including the shape anddimensions of the bayonet lugs 403 and 503. These cameras andinterchangeable lenses have a common mount structure which allows mutualengagement.

However, there are differences in length in the circumferentialdirection among the three bayonet lugs in the respective cameras andinterchangeable lenses. Thus, in a combination of mutually mountableinterchangeable lenses and cameras, the interchangeable lenses arecorrectly mountable in the cameras only when there is a phaserelationship in which the three bayonet lugs of the interchangeable lensare inserted among the three bayonet lugs of the camera. Indexes 208,308, 309, 408 and 509 serve as marks to recognize this phaserelationship.

FIG. 26 shows the first interchangeable lens 401 mounted on the firstcamera 201. In this case, the first lens-side index 408 provided on thefirst interchangeable lens 401 is aligned with the first lens mountingindex 208 provided on the first camera 201 and the bayonet lug 403 ofthe first interchangeable lens 401 is inserted between the bayonet lugs203 of the first camera 201. This causes the mount reference surfaces202 a, 402 a contact with each other. Next, the first interchangeablelens 401 is rotated by a predetermined angle with respect to the firstcamera 201 and the bayonet lugs 403 of the first interchangeable lens401 are thereby engaged with the bayonet lugs 203 of the first camera201 (the front end face of the bayonet lugs 403 come close contact withthe back end face of the bayonet lug 203) and the first interchangeablelens 401 is mounted on the first camera 201.

In this condition, the electric contact pins 204 of the first camera 201contact the electric contacts 404 of the first interchangeable lens 401,which allows communication between the two and power supply from thefirst camera 201 to the first interchangeable lens 401.

Next, FIG. 27 shows the second interchangeable lens 501 mounted on thesecond camera 301. In this case, as shown in FIG. 31, the secondlens-side index 509 provided on the second interchangeable lens 501 isaligned with the second lens mounting index 309 provided on the secondcamera 301 and the bayonet lugs 503 of the second interchangeable lens501 are inserted between the bayonet lugs 303 of the second camera 301.This causes the mount reference surfaces 302 a, 502 a to contact eachother.

At this time, as shown in FIG. 27, the protruding portion 505 of thesecond interchangeable lens 502 fits into (is inserted into) thecontaining portion 307 of the second camera 301. The distance from themount reference surface 302 a of the second camera 301 to the back endface 307 a of the containing portion 307 indicated by “F” in the figureis slightly larger than the protruding amount “B” of the protrudingportion 505 of the second interchangeable lens 501 and the back end faceof the protruding portion 505 does not contact the back end face 307 aof the containing portion 307. That is, the back end face 307 a of thecontaining portion 307 is provided at a position retreated from theprotruding portion 505 of the second interchangeable lens 501.

Next, the second interchangeable lens 501 is rotated by a predeterminedangle with respect to the second camera 301 and the bayonet lugs 503 ofthe second interchangeable lens 501 are thereby engaged with the bayonetlugs 303 of the second camera 301 (the front end face of the bayonet lug503 comes into close contact with the back end face of the bayonetlug303) and the second interchangeable lens 501 is mounted on the secondcamera 301.

In this condition, the electric contact pins 304 of the second camera301 contact the electric contacts 504 of the second interchangeable lens501, which allows communication between the two and power supply fromthe second camera 301 to the second interchangeable lens 501.

FIG. 28 shows a state in which an attempt is made to mount the secondinterchangeable lens 501 on the first camera 201. Here, as shown in FIG.32, the second lens-side index 509 provided on the secondinterchangeable lens 501 is aligned with the lens mounting index 208provided on the first camera 201 (in a phase relationship other than aspecific phase relationship).

In this case, as described above, the phase of the second lens-sideindex 509 on the second interchangeable lens 501 with respect to thebayonet lugs 503 is different from the phase of the first lens-sideindex 408 on the first interchangeable lens 401 with respect to thebayonet lugs 403, and therefore the bayonet lugs 503 of the secondinterchangeable lens 501 do not enter between the bayonet lugs 203 ofthe first camera 201, and the back end face of the bayonet lugs 503 ofthe second interchangeable lens 501 contacts the front end face of thebayonet lugs 203 of the first camera 201. The shaded area P in FIG. 32is the area in which both bayonet lugs 503, 203 contact each other.

At this time, as shown in FIG. 28, the back end face of the protrudingportion 505 of the second interchangeable lens 501 is positioned apartfrom the wall portion 205 of the first camera 201 by a distance “S”(that is, the back end face does not contact the wall portion 205). Thedistance S generally corresponds to the thickness of the bayonet lug503. Therefore, even when the second interchangeable lens 501 is rotatedwith respect to the first camera 201 in this condition, there is nopossibility that the wall portion 205 and protruding portion 505 may bedamaged due to friction between the wall portion 205 and the protrudingportion 505.

Such a condition occurs in a wide phase relationship in which the backend faces of the three bayonet lugs 503 of the second interchangeablelens 501 contact at least part of the three bayonet lugs 203 of thefirst camera 201 (wider than a case where there is a specific phaserelationship which will be described later). For this reason, in manycases where such wrong mounting is attempted, it is possible to preventthe wall portion 205 and protruding portion 505 from being damaged.Moreover, since the bayonet lugs are inherently strong (especially whenthe entire mount including the bayonet lugs is made of metal), nostrength-related problem will occur even when the second interchangeablelens 501 is rotated and pushed against the first camera 201.

In contrast, FIG. 29 shows a case where the second interchangeable lens501 and the first camera 201 have a phase relationship (the specificphase relationship) in which as shown in FIG. 33, all the three bayonetlugs 503 provided in the second interchangeable lens 501 are insertedbetween the three bayonet lugs 203 provided in the first camera 201. Forexample, this is a case where the user rotates the secondinterchangeable lens 502 from the state shown in FIG. 28 and FIG. 32 tothe state shown in FIG. 29 and FIG. 33.

In this case, the back end face of the protruding portion 505 of thesecond interchangeable lens 501 contacts the wall portion 205 of thefirst camera 201. The end faces in the circumferential direction of thebayonet lugs 503 of the second interchangeable lens 501 and the bayonetlugs 203 of the first camera 201 come closer to or contact each other(located at substantially the same positions in the direction of theoptical axis and at least partially overlap when viewed from thecircumferential direction) For this reason, when the back end face ofthe protruding portion 505 contacts the wall portion 205, the secondinterchangeable lens 501 is prevented from being mounted on the firstcamera 201, the end faces in the circumferential direction of thebayonet lugs 503, 203 contact each other and unnecessary rotation of thesecond interchangeable lens 501 with respect to the first camera 201 isthereby prevented. Therefore, even if the back end face of theprotruding portion 505 contacts the wall portion 205, it is possible toprevent the wall portion 205 and the protruding portion 505 from beingdamaged whenever possible.

As shown in FIG. 34, FIG. 35 and FIG. 36, there may be cases where oneof the three bayonet lugs 503 of the second interchangeable lens 501 areinserted between some of the three bayonet lugs 203 of the first camera201 (another example of the specific phase relationship). This is anintermediate state between the state shown in FIG. 29 and FIG. 33 andthe state shown in FIG. 28 and FIG. 32. The back end face of at leastone (e.g., bayonet lug 503 in the upper part of FIG. 36) of the twobayonet lugs other than the bayonet lug which enters between the bayonetlugs 203 of the first camera 201 out of the three bayonet lugs 503 ofthe second interchangeable lens 501 contacts the front end face of thebayonet lugs 203 of the first camera 201 diagonally (the range in whichsuch contact may occur is indicated by the shaded area P in FIGS. 34 and35).

In this case, too, since part of the protruding portion 505 on the sideof the inserted bayonet lug 503 (lower part in FIG. 36) contacts thewall portion 205 of the first camera 201, further movement in thedirection for which the second interchangeable lens 501 is mounted onthe first camera 201 is prevented. Furthermore, the end faces in thecircumferential direction of the inserted bayonet lug 503 and thebayonet lugs 203 of the first camera 201 which sandwich the insertedbayonet lug 503 in the circumferential direction contact each other,which prevents unnecessary rotation of the second interchangeable lens301. Therefore, it is possible to prevent the wall portion 205 andprotruding portion 505 from being damaged whenever possible.

As explained above, the protruding amount B of the protruding portion505 of the second interchangeable lens 501 from the mount referencesurface 502 a is set under the following two conditions:

(1) When the second interchangeable lens 501 has a specific phaserelationship with the first camera 201 (phase relationship shown inFIGS. 29, 33 and FIGS. 34 to 36), the back end face of the protrudingportion 505 should contact the wall portion 205 of the first camera 201,and

(2) When the second interchangeable lens 501 has a phase relationshipother than the specific phase relationship with the first camera 201(e.g., the phase relationship shown in FIGS. 28 and 32) and the imageplane side surface (back end face) of the bayonet lug 503 of the secondinterchangeable lens 501 contacts (the front end face of) the bayonetlug 203 of the first camera 201, the back end face of the protrudingportion 505 should draw away from the wall portion 205.

That is, when the second interchangeable lens 505 and the first camera201 have a phase relationship other than the specific phaserelationship, the bayonet lugs contact each other in the direction ofthe optical axis, and therefore the protruding portion 505 of the secondinterchangeable lens 501 does not contact the wall portion 205 of thefirst camera 201, and can thereby prevent the second interchangeablelens 505 from being mounted on the first camera 201.

For example, when an attempt is made to align the second lens-side index509 provided on the second interchangeable lens 501 with the lensmounting index 208 on the first camera 201 to couple the lens andcamera, since their bayonet lugs contact each other in the direction ofthe optical axis, the mounting is prevented.

For this reason, in many cases where attempts are made to mount thesecond interchangeable lens 501 on the first camera 201, it is possibleto prevent such mounting and further prevent the wall portion 205 andthe protruding portion 505 from being damaged caused by the protrudingportion 505 contacting the wall portion 205. Moreover, this is a casewhere the bayonet lugs contact each other, and therefore there is noproblem in the aspect of strength.

Furthermore, the mounting is prevented because the protruding portion505 contacts the wall portion 205 only when the second interchangeablelens 501 and the first camera 201 have the specific phase relationship.However, in this case, too, contact between the bayonet lugs in thecircumferential direction can prevent unnecessary rotation of the secondinterchangeable lens 501 with respect to the first camera 201, thuseliminating the possibility that the wall portion 205 may be damaged.

In FIGS. 38 and 39, an embodiment is shown wherein a rubber ring 506which is an elastic member is provided on the back end of the protrudingportion 506 of the second interchangeable lens 501 (mount 502). Therubber ring 506 covers the entire outer circumstantial side part of theback end face of the protruding portion 505.

The back end face of the rubber ring 506 protrudes slightly backwardfrom the portion on the inner diameter side of the rubber ring 506 (backend face of the lens holding member 513 shown in FIG. 25). In this way,even when the protruding portion 505 of the second interchangeable lens501 can contact the wall portion 205 of the first camera 201 in theabove described specific phase relationship, the rubber ring 506contacts the wall portion 205 first and the elasticity thereof caneffectively prevent the wall portion 205 and protruding portion 505 frombeing damaged.

Furthermore, the above described embodiments have explained the casewhere the protruding portion 505 of the second interchangeable lens 501(mount 502) is ring-shaped, but as shown in FIG. 40 and FIG. 41, it isalso possible to form the protruding portions 505′, 505″ divided intotwo or three portions in the circumferential direction. In this case,too, the elastic member may be attached so as to cover the back endfaces of the protruding portions 505′, 505″.

According to the foregoing embodiments, without changing the shape anddimensions of bayonet lugs of the first and second camera, theprotruding portion of the second interchangeable lens contacts the firstwall portion only when the second interchangeable lens and the firstcamera have a specific phase relationship, and it is possible to therebyprevent the second interchangeable lens from being mounted on the firstcamera. Furthermore, when the second interchangeable lens and the firstcamera have a phase relationship other than the specific phaserelationship, the surface on the image plane side of the bayonet lug ofthe second interchangeable lens contacts the bayonet lugs of the firstcamera, thus preventing the second interchangeable lens from beingmounted on the first camera, preventing the protruding portion of thesecond interchangeable lens from contacting the first wall portion andthereby avoiding the first wall portion and protruding portion frombeing damaged. Moreover, since this is the case of contact between thebayonet lugs, even if the second interchangeable lens is rotated andpushed against the first camera, there is no problem in the aspect ofstrength.

Furthermore, according to the foregoing embodiments, when an attempt ismade to align the lens-side index provided on the second interchangeablelens with the camera-side index provided on the first camera and couplethe lens and camera, the surface on the image plane side of the bayonetlug of the second interchangeable lens contacts the bayonet lug of thefirst camera, and therefore it is possible to prevent the mountingwithout changing the shape and dimensions of the bayonet lugs in thefirst and second cameras. This is also the case of contact between thebayonet lugs, and therefore even if the second interchangeable lens ispushed against the first camera, there is no problem in the aspect ofstrength.

Note that since the elastic member is provided at the end of theprotruding portion of the second interchangeable lens, even if anattempt is made to erroneously mount the second interchangeable lens onthe first camera, it is possible to protect the first camera and secondinterchangeable lens even when the protruding portion of the secondinterchangeable lens contacts the first wall portion of the firstcamera.

While preferred embodiments have been described, it is to be understoodthat modification and variation of the present invention may be madewithout departing from the scope of the following claims.

This application claims priorities from Japanese Patent Applications No.2003-329193 filed on Sep. 19, 2003, No. 2003-205284 filed on Aug. 1,2003 and 2003-206183 filed on Aug. 6, 2003, which are herebyincorporated by reference herein.

1. An interchangeable lens which is the following second interchangeablelens used in a camera system including a first interchangeable lens, thesecond interchangeable lens, a first camera and a second camera, theinterchangeable lens comprising: a protruding portion protruding from amount reference surface toward an image plane, the protruding amount ofthe protruding portion being larger than that of the firstinterchangeable lens, and the second interchangeable lens having thesame flange back as that of the first interchangeable lens, wherein thefirst camera includes a first wall portion inside its mount, the firstinterchangeable lens is mounted on the first camera through bayonetcoupling, and the first camera prevents mounting on the secondinterchangeable lens by the protruding portion of the secondinterchangeable lens contacting the first wall portion, and the secondcamera includes a second wall portion provided at a position retreatedfrom the protruding portion of the second interchangeable lens insideits mount, the second camera includes a bayonet lug are having the sameshape and dimensions as a bayonet lug of the first camera, and the firstand second interchangeable lenses are mounted on the second camerathrough bayonet coupling, wherein the protruding amount of theprotruding portion of the second interchangeable lens is set, in a casewhere the second interchangeable lens has a specific phase relationshipwith the first camera, so that the protruding portion contacts the firstwall portion, and the protruding amount of the protruding portion of thesecond interchangeable lens is set, in a case where the secondinterchangeable lens has a phase relationship other than the specificphase relationship with the first camera and an image plane side surfaceof a bayonet lug of the second interchangeable lens is in contact withthe bayonet lug of the first camera, so that the protruding portion isaway from the first wall portion.
 2. An interchangeable lens which isthe following second interchangeable lens whose flange back is the sameas that of a first interchangeable lens, comprising: a protrudingportion protruding from a mount reference surface toward an image plane,wherein the protruding amount of the protruding portion is larger thanthat of the first interchangeable lens, mounting of the secondinterchangeable lens on the first camera having a first wall portioninside its mount is prevented by the protruding portion contacting thefirst wall portion, the first camera is a camera on which the firstinterchangeable lens is mounted through bayonet coupling, mounting ofthe second interchangeable lens on the second camera is realized throughbayonet coupling, the second camera is a camera whose bayonet lug hasthe same shape and dimensions as a bayonet lug of the first camera, thefirst interchangeable lens is mounted on the second camera throughbayonet coupling, and the second camera includes a second wall portionprovided at a position retreated from the protruding portion of thesecond interchangeable lens inside its mount, wherein the protrudingamount of the protruding portion of the second interchangeable lens isset, in a case where the second interchangeable lens has a specificphase relationship with the first camera, so that the protruding portioncontacts the first wall portion, and the protruding amount of theprotruding portion of the second interchangeable lens is set, in a casewhere the second interchangeable lens has a phase relationship otherthan the specific phase relationship with the first camera and an imageplane side surface of a bayonet lug of the second interchangeable lensis in contact with the bayonet lug of the first camera, so that theprotruding portion is away from the first wall portion.
 3. Theinterchangeable lens according to claim 1, wherein an optical lens isarranged inside the protruding portion of the second interchangeablelens, and a back focus of the second interchangeable lens is shorterthan a back focus of the first interchangeable lens.
 4. Theinterchangeable lens according to claim 2, wherein an optical lens isarranged inside the protruding portion of the second interchangeablelens, and a back focus of the second interchangeable lens is shorterthan a back focus of the first interchangeable lens.
 5. Theinterchangeable lens according to claim 1, further comprising: alens-side index which serves as a mark for determining a phaserelationship with the second camera when the second interchangeable lensis mounted on the second camera, wherein in a case where the secondinterchangeable lens has such a phase relationship with the first cameraincluding a camera-side index which serves as a mark for determining aphase relationship with the first interchangeable lens when the firstinterchangeable lens is mounted on the first camera that the lens-sideindex matches the camera-side index, the image plane side surface of thebayonet lug of the second interchangeable lens contacts the bayonet lugof the first camera to thereby prevent the second interchangeable lensfrom being mounted on the first camera.
 6. The interchangeable lensaccording to claim 2, further comprising: a lens-side index which servesas a mark for determining a phase relationship with the second camerawhen the second interchangeable lens is mounted on the second camera,wherein in a case where the second interchangeable lens has such a phaserelationship with the first camera including a camera-side index whichserves as a mark for determining a phase relationship with the firstinterchangeable lens when the first interchangeable lens is mounted onthe first camera that the lens-side index matches the camera-side index,the image plane side surface of the bayonet lug of the secondinterchangeable lens contacts the bayonet lug of the first camera tothereby prevent the second interchangeable lens from being mounted onthe first camera.
 7. The interchangeable lens according to claim 1,wherein an elastic member is provided at the end on an image plane sidein the protruding portion of the second interchangeable lens.
 8. Theinterchangeable lens according to claim 2, wherein an elastic member isprovided at the end on an image plane side in the protruding portion ofthe second interchangeable lens.
 9. An interchangeable lens which is thefollowing second interchangeable lens used in a camera system includinga first interchangeable lens, the second interchangeable lens, a firstcamera and a second camera, the interchangeable lens comprising: aprotruding portion protruding from a mount reference surface toward animage plane, the protruding amount of the protruding portion beinglarger than that of the first interchangeable lens, and the secondinterchangeable lens having the same flange back as that of the firstinterchangeable lens, wherein the first camera includes a first wallportion inside its mount, the first interchangeable lens is mounted onthe first camera through bayonet coupling and the first camera preventsmounting of the second interchangeable lens by the protruding portion ofthe second interchangeable lens contacting the first wall portion, thefirst camera includes a camera-side index which serves as a mark fordetermining a phase relationship with the first interchangeable lenswhen the first interchangeable lens is mounted on the first camera, thesecond camera includes a second wall portion provided at a positionretreated from the protruding portion of the second interchangeable lensinside its mount, and includes a bayonet lug whose shape and dimensionsare the same as a bayonet lug of the first camera, and the first andsecond interchangeable lenses are mounted on the second camera throughbayonet coupling, the second interchangeable lens further comprising alens-side index which serves as a mark for determining a phaserelationship with the second camera when the second interchangeable lensis mounted on the second camera, wherein in a case where the secondinterchangeable lens has such a phase relationship with the first camerathat the lens-side index matches the camera-side index, an image planeside surface of a bayonet lug of the second interchangeable lenscontacts the bayonet lug of the first camera to thereby prevent thesecond interchangeable lens from being mounted on the first camera. 10.An interchangeable lens which is the following second interchangeablelens whose flange back is the same as that of a first interchangeablelens, comprising: a protruding portion protruding from a mount referencesurface toward an image plane; wherein the protruding amount of theprotruding portion is larger than that of the first interchangeablelens, mounting of the second interchangeable lens on a first camerahaving a first wall portion inside its mount is prevented by theprotruding portion contacting the first wall portion, the first camerais a camera on which the first interchangeable lens is mounted throughbayonet coupling, and the first camera includes a camera-side indexwhich serves as a mark for determining a phase relationship with thefirst interchangeable lens when the first interchangeable lens ismounted the first camera, mounting of the second interchangeable lens onthe second camera is realized through bayonet coupling, the secondcamera includes a bayonet lug whose shape and dimensions are the same asa bayonet lug of the first camera, the first interchangeable lens ismounted on the second camera through bayonet coupling and the secondcamera includes a second wall portion provided at a position retreatedfrom the protruding portion of the second interchangeable lens insideits mount, the second interchangeable lens further comprising alens-side index which serves as a mark for determining a phaserelationship with the second camera when the second interchangeable lensis mounted on the second camera, wherein in a case where the secondinterchangeable lens has such a phase relationship with the first camerathat the lens-side index matches the camera-side index, an image planeside surface of a bayonet lug of the second interchangeable lenscontacts the bayonet lug of the first camera to thereby prevent thesecond interchangeable lens from being mounted on the first camera. 11.The interchangeable lens according to claim 9, wherein an optical lensis arranged inside the protruding portion of the second interchangeablelens, and a back focus of the second interchangeable lens is shorterthan a back focus of the first interchangeable lens.
 12. Theinterchangeable lens according to claim 10, wherein an optical lens isarranged inside the protruding portion of the second interchangeablelens, and a back focus of the second interchangeable lens is shorterthan a back focus of the first interchangeable lens.
 13. Aninterchangeable lens system comprising: the interchangeable lens whichis the following second interchangeable lens according to claim 1 usedfor a camera system including a first interchangeable lens, the secondinterchangeable lens, a first camera and a second camera; and the firstinterchangeable lens, wherein the interchangeable lens system is usedfor a camera group including the first and second cameras provided withan image-pickup element which photoelectrically converts an objectimage.
 14. An interchangeable lens system comprising: theinterchangeable lens according to claim 2 which is mounted on a secondcamera out of a first camera and the second camera on which a firstinterchangeable lens is mounted in common; and the first interchangeablelens, wherein the interchangeable lens system is used for a camera groupincluding the first and second cameras provided with an image-pickupelement which photoelectrically converts an object image.
 15. Aninterchangeable lens system comprising: the interchangeable lensaccording to claim 9 used for a camera system including a firstinterchangeable lens, a first camera and a second camera; and the firstinterchangeable lens, wherein the interchangeable lens system is usedfor a camera group including the first and second cameras provided withan image-pickup element which photoelectrically converts an objectimage.
 16. An interchangeable lens system comprising: theinterchangeable lens according to claim 10 which is mounted on a secondcamera out of a first camera and the second camera on which a firstinterchangeable lens is mounted in common; and the first interchangeablelens, wherein the interchangeable lens system is used for a camera groupincluding the first and second cameras provided with an image-pickupelement which photoelectrically converts an object image.
 17. A camerasystem comprising: a first interchangeable lens; a secondinterchangeable lens having a protruding portion protruding from a mountreference surface toward an image plane, the protruding amount of theprotruding portion being larger than that of the first interchangeablelens, and the second interchangeable lens having the same flange back asthat of the first interchangeable lens; a first camera including a firstwall portion inside its mount, the first interchangeable lens beingmounted on the first camera through bayonet coupling and the firstcamera preventing mounting of the second interchangeable lens by theprotruding portion of the second interchangeable lens contacting thefirst wall portion; a second camera, including a second wall portionprovided at a position retreated from the protruding portion of thesecond interchangeable lens inside its mount, having a bayonet lug whoseshape and dimensions are the same as a bayonet lug of the first camera,and the first and second interchangeable lens being mounted on thesecond camera through bayonet coupling, wherein the protruding amount ofthe protruding portion of the second interchangeable lens is set, in acase where the second interchangeable lens has a specific phaserelationship with the first camera, so that the protruding portion ofthe second interchangeable lens contacts the first wall portion, and theprotruding amount of the protruding portion of the secondinterchangeable lens is set, in a case where the second interchangeablelens has a phase relationship other than the specific phase relationshipwith the first camera and an image plane side surface of a bayonet lugof the second interchangeable lens is in contact with the bayonet lug ofthe first camera, so that the protruding portion of the secondinterchangeable lens is away from the first wall portion.
 18. The camerasystem according to claim 17, wherein the second interchangeable lens isprovided with an optical lens inside the protruding portion and has aback focus shorter than a back focus of the first interchangeable lens.19. The camera system according to claim 17, wherein the first cameraincludes a camera-side index which serves as a mark for determining aphase relationship with the first interchangeable lens when the firstinterchangeable lens is mounted on the first camera, the secondinterchangeable lens includes a lens-side index which serves as a markfor determining a phase relationship with the second camera when thesecond interchangeable lens is mounted on the second camera, and in acase where the second interchangeable lens has such a phase relationshipwith the first camera that the lens-side index matches the camera-sideindex, the image plane side surface of the bayonet lug of the secondinterchangeable lens contacts the bayonet lug of the first camera tothereby prevent the second interchangeable lens from being mounted onthe first camera.
 20. The camera system according to claim 17, whereinan elastic member is provided at the end on an image plane side of theprotruding portion of the second interchangeable lens.
 21. A camerasystem comprising: a first interchangeable lens; a secondinterchangeable lens including a protruding portion protruding from amount reference surface toward an image plane, the protruding amount ofthe protruding portion being larger than that of the firstinterchangeable lens, and the second interchangeable lens having thesame flange back as that of the first interchangeable lens; a firstcamera including a first wall portion inside its mount, the firstinterchangeable lens being mounted on the first camera through bayonetcoupling and the first camera preventing mounting of the secondinterchangeable lens by the protruding portion of the secondinterchangeable lens contacting the first wall portion, the first cameraincluding a camera-side index which serves as a mark for determining aphase relationship with the first interchangeable lens when the firstinterchangeable lens is mounted on the first camera, and; a secondcamera including a second wall portion provided at a position retreatedfrom the protruding portion of the second interchangeable lens insideits mount, having a bayonet lug whose shape and dimensions are the sameas a bayonet lug of the first camera, and the first and secondinterchangeable lens are mounted on the second camera through bayonetcoupling, the second interchangeable lens including a lens-side indexwhich serves as a mark for determining a phase relationship with thesecond camera when the second interchangeable lens is mounted on thesecond camera, wherein in a case where the second interchangeable lenshas such a phase relationship with the first camera that the lens-sideindex matches the camera-side index, an image plane side surface of abayonet lug of the second interchangeable lens contacts the bayonet lugof the first camera to thereby prevent the second interchangeable lensfrom being mounted on the first camera.
 22. The camera system accordingto claim 21, wherein the second interchangeable lens is provided with anoptical lens inside the protruding portion and has a back focus shorterthan a back focus of the first interchangeable lens.
 23. Aninterchangeable lens which is not mountable on a first camera having afirst wall portion inside its mount and which is mountable on a secondcamera having a second wall portion inside its mount and including abayonet lug having the same shape and dimensions as a bayonet lug of thefirst camera, the interchangeable lens comprising: a lens side mountincluding a lens-side bayonet lug corresponding to the bayonet lugs ofthe mounts of the first and second cameras; and a protruding portionprotruding from a reference surface of the lens side mount toward animage plane, wherein the protruding amount of the protruding portion isset, in a case where the interchangeable lens has a specific phaserelationship with the first camera, so that the protruding portioncontacts the first wall portion, and the protruding amount is set, in acase where the interchangeable lens has a phase relationship with thefirst camera other than the specific phase relationship and an imageplane side surface of the bayonet lug of the interchangeable lens is incontact with the bayonet lug of the first camera, so that the protrudingportion is away from the first wall portion.